You don't need a graflock back. The Polaroid 405 holder, which is in my experience far more common used than the Fuji, fits in a spring back and takes the 3.25x4.25 film just fine. As a bonus, the film is much less expensive, less than a dollar a shot in the US, than the 4x5 was even before it was canceled. I elected to go this route even when the 4x5 was available because the image area is quite large enough and close enough for proofing, or even shooting for itself if you like and compose accordingly, the film was 1/3 the price, and I can use the same film packs in my Mamiya 645 Pro Polaroid back.
Originally Posted by Heinz
I should say it fits some spring backs, maybe. It is pretty thick and it's a tight fit in my Tech III and I occasionally waste a sheet when the dark slide gets stuck and removing the back pulls it out as well - but I'm getting better about remembering to use both hands and do this carefully.
The stuff is kind of addictive. The color is vibrant but does tend to go blue easily. I need to get the equivalent of a skylight or slight warming filter for my 3x3 filter holder for the 4x5, to use this stuff.
Do be aware that most of the backs available have long ago lost the overlay for a 4x5 ground glass and the image area is NOT centered in the 4x5 frame - it's offset mainly vertically. But there are .pdf templates you can download to cut out your own mask.
Here's one I took this week. We were attending my wife's family reunion and staying at a lake house in Alabama. I shot this off the back deck. Linhof Tech III, 90mm Angulon, 1/100th f/16.
AL_LakeHouse1 by Roger Cole, on Flickr